The present invention relates to a flexible IC module which is a basis for information carriers such as contactless IC cards, a method for producing the flexible IC module, and a method for producing information carriers using the flexible IC module.
Use of contactless information carriers such as contactless IC cards as substitutes for commutation tickets, driver""s licenses, telephone cards and cash cards has been investigated, and since extensive use thereof has been expected, one of the most important technical tasks is how to simplify the production steps and reduce the unit cost.
Hitherto, as a method for producing contactless IC cards, there has been known a method which comprises boring holes through a reinforcing material made of glass fiber or the like, storing an IC chip and a coil which is a contactless signal transmission means in the hole, then sealing the hole with a resin to form a substrate, and finally applying cover sheets to the front and back sides of the substrate to obtain the desired contactless IC cards.
According to this method, contactless IC cards in which the position of the coil set in the substrate is accurately regulated can be produced by adjusting the size of the bored hole to a suitable size depending on the size of the coil. Thus, transfer of power and signal between the IC card and the external devices can be performed highly efficiently.
As another method, as disclosed in, for example, NIKKEI MECHANICAL 1997. 1.6, No.497, pp.16-17, a method is proposed which comprises disposing a first resin sheet to which an IC chip and a coil as a contactless data transmission means are bonded and a second resin sheet having no such IC chip and coil at facing portions of a stationary mold and a movable mold of an injection molding machine, respectively, putting the molds together, and then filling a cavity with a resin whereby a contactless IC card comprising the first and second resin sheets, the IC chip and the coil which are integrated with the filling resin is obtained.
According to this method, since a contactless IC card having resin sheets (cover sheets) bonded to the front and back sides can be obtained by injection molding, the contactless IC card can be more efficiently produced and the production cost can be reduced as compared with the conventional method according to which a substrate in which IC chip and coil are embedded is cured and thereafter cover sheets are bonded to the front and back sides of the substrate.
On the other hand, as for the connection of IC chip and coil mounted on the contactless IC card, generally is employed a method of mounting the IC chip on a wiring substrate and connecting the coil to an electrode terminal formed on the wiring substrate.
This method has been technically established and hence the IC chip and the wiring substrate, and the wiring substrate and the coil can be connected with a high reliability.
However, in the former method of the above-mentioned conventional methods for the production of contactless IC cards, IC chip and coil are stored in a hole bored in a reinforcing material, and then inside and outside of the hole are cured with resin. Therefore, the inside of the hole having no reinforcing material is low in strength, and stress is concentrated at the inside of the hole and the substrate is apt to be broken when an improper external force such as bending is applied.
Furthermore, since sealing of the hole with resin and impregnation of the reinforcing material with resin and curing of the reinforcing material must be carried out after the IC chip and the coil are accurately set in the reinforcing material in which the desired hole is bored, the production steps are complicated and cheap information carriers can hardly be produced. Especially, when various contactless IC cards are produced on the same line, various reinforcing materials differing in the size of the holes depending on the size of the IC chip and the coil stored therein. Thus, the production steps are further complicated, resulting in increase of the production cost of contactless IC cards.
On the other hand, since the latter method of the above-mentioned conventional methods for the production of contactless IC cards carries out injection molding with a cover sheet having an IC chip and a coil which are bonded thereto being disposed on one of the molds, a molten resin of high temperature contacts with the portions of the cover sheet to which an adhesive is applied and not applied. Therefore, it has been found that owing to the difference in coefficient of thermal expansion of the portions to which the adhesive is applied and not applied, wrinkles are apt to be formed at the boundary of these portions. According to experiments, it was difficult to produce contactless IC cards having no wrinkles on the cover sheets even when resin temperature, injection speed and injection pressure were variously changed.
Since contactless IC cards are handled by fingers and directly viewed, those having wrinkles on the surface are not good in hand and appearance and lose commercial value. Furthermore, in case the surface of the cover sheet is printed after the production of contactless IC cards, it is impossible to perform beautiful printing on the surface of the cards and they also have no commercial value.
Moreover, the conventional connection method of IC chip and coil requires a wiring substrate as an essential constitutive element. Therefore, it needs a high cost, and it is difficult to make thinner and flexible the contact less IC cards.
The present invention has solved these problems, and the objects of the present invention are to provide a construction of a flexible IC module which makes easy to produce information carriers, to provide a method for producing the flexible IC module at low cost and at high efficiency, and to provide a method for producing an information carrier superior in feeling at use and excellent in appearance at low cost and at high efficiency using the above flexible IC module.
 less than Construction of Flexible IC Module greater than 
In order to solve the above problems, as for the construction of the flexible IC module, the present invention employs such construction as comprising a flexible substrate of a given shape and a given size having compressibility in the thickness direction, self-pressure bonding property and resin impregnation property and parts mounted and carried on the flexible substrate, the parts to be mounted being embedded in dents formed by compression in a portion of the flexible substrate.
The parts to be mounted can be completely embedded in the flexible substrate or can be embedded in one side of the flexible substrate ehilr being partly exposed outside. In the former case, the front and back sides of the flexible substrate are formed in a planar state, and in the latter case, the front and back sides of the flexible substrate including the surface of the embedded parts embedded are formed in a planar state.
In the present specification, a xe2x80x9cself-pressure bonding propertyxe2x80x9d means such characteristics of the flexible substrate that when a compressive force is applied to the flexible substrate at room temperature or under heating, the fibers constituting the flexible substrate are bonded or when a compressive force is applied to a plurality of stacked flexible substrates, these flexible substrates are bonded to each other, and the flexible substrate(s) are kept at the state of the volume being reduced than before application of the compressive force.
As woven fabrics, knitted fabrics or nonwoven fabrics which per se have the self-pressure bonding property, there may be used those which comprise so-called conjugate fibers each of which is composed of two or more parts differing in melting point; those which are obtained by mixed spinning two or more synthetic resins differing in melting point or which are mixtures of synthetic resin fibers differing in melting point; and those which comprise glass fibers, carbon fibers, Kepler fibers, chemical fibers, natural fibers or combination thereof, these fibers being bonded to each other with a resin binder. As woven fabrics, knitted fabrics, nonwoven fabrics or paper to which the self-pressure bonding property is imparted by impregnating them with a suitable amount of synthetic resin, there may be used those which comprise glass fibers, carbon fibers, Kepler fibers, chemical fibers, natural fibers or combination thereof. As the nonwoven fabrics, there may be used all of the nonwoven fabrics having the known structure such as, for example, those which comprise a web composed of random fibers obtained by opening synthetic resin filaments prepared by melt spinning and those which comprise a web having a fine reticulate structure made of synthetic resin fibers prepared by injecting a solution of starting polymer.
If necessary, a desired circuit pattern can be printed on the surface of the flexible substrate on which parts are mounted, and this circuit pattern can include a coil for transmission of data and/or electric source.
The parts to be mounted and carried on the flexible substrate include, for example, at least one parts selected from an IC chip, an IC module, a contactless transmission means for data and/or electric source, a condenser, a resistor, a solar battery, an image display device, an optical recording medium, an optical magnetic recording medium, a transparent code information display device formed using an infrared absorber, an infrared emitter or a phosphor, and a magnet or ferromagnet for highly accurately positioning an information carrier at the portion at which a carrier for reader-writer is set, and combination of these parts with other parts. A coil can be used as the contactless transmission means for data and/or electric source. A preferred wire for constituting the coil comprises a core wire of copper, aluminum or the like, a bonding metal layer such as gold or solder which covers the core wire, and an insulating layer such as polyurethane which covers the bonding metal layer for attaining easy connection with other electronic parts such as an IC chip.
Furthermore, when an IC chip and a coil are mounted as the parts, it is preferred to directly connect both ends of the coil to the input and output terminals of the IC chip for decreasing the thickness of the flexible IC module and reducing the cost. For the direct connection of the IC chip and the coil, wedge bonding method can be employed, but according to this method, there are the following problems: {circle around (1)} since the pressed portion of the coil is deformed to flat by applying ultrasonic and high pressure to the connecting portion, burnout sometimes occurs at the boundary portion between the deformed portion and the undeformed portion; {circle around (2)} since ultrasonic and high pressure are applied to the connecting portion, the IC chip is sometimes damaged, and especially when a thin chip of about 50-150 xcexcm thick is used, the damage is conspicuous; {circle around (3)} since the ultrasonic which requires complicated setting of conditions, control of the connecting conditions is difficult and it is difficult to produce non-defective articles stably. Therefore, it is particularly preferred to employ the soldering method or welding method which is free from these problems.
The soldering of coil to IC chip can be carried out by the method according to which an IC chip having a solder bump previously formed at the input and output terminals is used, the both ends of the coil for contactless transmission are allowed to contact with the solder bumps, then a bonding tool is pressed to the both ends of the coil and the solder bumps are molten by the energy given from the bonding tool. On the other hand, the welding of the coil to the IC chip can be carried out by a method according to which an IC chip having gold bumps previously formed at the input and output terminals is used, the both ends of the coil for contactless transmission are allowed to contact with the gold bumps, then a welding head is pressed to both ends of the coil and the gold bumps are molten by the energy given from the welding head.
The bonding tool for the soldering and the welding head for the welding which can heat the connecting metal to higher than the melting temperature are enough and those of the same construction can be used.
In the flexible IC module having the above construction, the parts to be mounted are embedded in the substrate such as nonwoven fabric, and thus the module is superior in the effect to protect the mounted parts. Moreover, since the substrate is formed of a nonwoven fabric or the like which can be impregnated with resin, the desired information carriers such as contactless IC cards and others can be produced by impregnating the substrate with resin and bonding the cover sheet by the impregnated resin. In this case, the substrate can be impregnated with the resin nearly uniformly, and hence no wrinkles are formed on the surface of the substrate and information carriers of high commercial value can be produced. Furthermore, in the IC module of the present construction, the substrate is composed of nonwoven fabric or the like which is very high in flexibility, and therefore it can be utilized not only as a constitutive part of flat information carriers, but also as an information carrier provided at the curved portion or the portion subjected to repeated deformation.
 less than Method for the Production of Flexible IC Module greater than 
The methods for the production of the flexible IC module are as follows:
{circle around (1)} A first flexible substrate and a second flexible substrate of a give shape and a given size which have compressibility in the thickness direction, self-pressure bonding property and resin impregnation property are prepared. Thereafter, the desired parts to be mounted are positioned and disposed between the first and second flexible substrates. Then, these first and second flexible substrates are compressed in the thickness direction at room temperature or under heating, thereby to integrate the first and second flexible substrates and simultaneously the parts to be mounted are embedded in the dents formed in the substrates by the application of compressive force.
{circle around (2)} The desired parts to be mounted are positioned and disposed on one side of a flexible substrate. Thereafter, the flexible substrate is compressed in the thickness direction at room temperature or under heating and the parts to be mounted are embedded in the dents formed by the compression in the flexible substrate.
According to the above methods {circle around (1)} and {circle around (2)}, the desired flexible IC module can be obtained only by stacking the necessary materials and parts and then compressing the resulting laminate in the thickness direction at room temperature or under heating. Thus, production of flexible IC modules can be performed at a very high efficiency.
{circle around (3)} An IC chip is positioned and disposed on one side of a first flexible substrate. Separately, a coil is positioned and disposed on one side of a second flexible substrate, and the both ends of the coil are set at the distance set between the input and output terminals provided at the IC chip. Then, the first and second flexible substrates are superposed so that the side of the first flexible substrate on which the IC chip is disposed and the side of the second flexible substrate on which the coil is disposed face each other and the input and output terminals of the IC chip contact with the both ends of the coil. These first and second flexible substrates are compressed in the thickness direction at room temperature or under heating, thereby to integrate the first and second flexible substrates and simultaneously the IC chip and the coil are embedded in the dents formed in a portion of the first and second substrates by the application of compressive force. Furthermore, heat and pressing force are applied to the input and output terminal portions from the outer surface of the second flexible substrate provided with the coil to electrically connect the input and output terminal portions and the both end portions of the coil with each other.
{circle around (4)} A coil is positioned and disposed on one side of a flexible substrate of a give shape and a given size which has compressibility in the thickness direction, self-pressure bonding property and resin impregnation property, and the both ends of the coil are set at the distance set between the input and output terminals provided at an IC chip. Then, an IC chip is disposed on one side of said flexible substrate with the input and output terminals being allowed to contact with the both end portions of the coil. This flexible substrate is compressed in the thickness direction at room temperature or under heating, and the IC chip and the coil are embedded in the dents formed in the flexible substrate by the application of compressive force. Furthermore, heat and pressing force are applied to the input and output terminal portions from the outer surface of the flexible substrate provided with the coil to electrically connect the input and output terminal portions and the both end portions of the coil with each other.
According to the methods {circle around (3)} and {circle around (4)}, an IC chip and a coil the both ends of which are directly connected to the input and output terminals of the IC chip are used as the parts to be mounted, and thus a thin IC module can be produced. Furthermore, since both end portions of the coil are previously fixed on the flexible substrate and the distance between the end portions is set to be equal to the distance set between the input and output terminals of the IC chip, the connection of the IC chip and the coil is easy and a flexible IC module can be efficiently produced.
 less than Method for the Production of Information Carrier greater than 
The methods for the production of information carrier are as follows:
{circle around (1)} The information carrier is produced by a method comprising the steps of disposing a first cover sheet and a second cover sheet at the predetermined portions of a stationary mold and a movable mold of a molding apparatus, respectively; superposing a flexible IC module on the cover sheet disposed at the stationary mold or the movable mold; closing the stationary mold and the movable mold and filling a resin in the cavity formed by the molds; and uniformly impregnating the flexible substrate with the filled resin, then opening the stationary mold and the movable mold and removing the information carrier which is the desired product.
According to this method, bonding of the parts to be mounted to the cover sheet can be omitted. Thus, the production of information carrier can be efficiently carried out and besides the heat load applied to the cover sheet at the time of filling of the resin can be uniformized, and wrinkling of the cover sheet caused by non-uniform heat load can be prevented. Accordingly, information carriers of high quality can be produced at a high efficiency and, besides, satisfactory design printing and the like can be performed. Furthermore, since the resin is filled while the parts to be mounted which are supported by the flexible substrate are present between the two cover sheets, the set position of the parts in the thickness direction of the information carrier can be optionally adjusted by adjusting the thickness of the substrate. Moreover, since the parts to be mounted are supported by the flexible substrate, the effect of protecting the parts can be enhanced. Of course, since nonwoven fabric and the like which can be impregnated with resin are used, the resin can be rapidly filled to cause no deterioration of injection molding cycle.
{circle around (2)} The information carrier is produced by a method comprising the steps of stacking a first heat-meltable sheet, a flexible IC module and a second heat-meltable sheet in this order on an upper surface of a bottom force; pressing a top force onto the second heat-meltable sheet to compress the laminate of the flexible IC module and the first and second heat-meltable sheets in the thickness direction under heating, thereby to melt the first and second heat-meltable sheets; and impregnating the flexible IC module with the melt of the first and second heat-meltable sheets, followed by hot press molding the module to obtain an information carrier of a given thickness.
{circle around (3)} The information carrier is produced by a method comprising the steps of stacking a first cover sheet, a first heat-meltable sheet, a flexible IC module, a second heat-meltable sheet and a second cover sheet in this order on an upper surface of a bottom force; pressing a top force onto the second cover sheet to compress the laminate of the flexible IC module, the first and second heat-meltable sheets and the first and second cover sheets in the thickness direction under heating, thereby to melt the first and second heat-meltable sheets; and impregnating the flexible IC module with the melt of the first and second heat-meltable sheets and simultaneously bonding the first and second cover sheets by the melt, followed by hot press molding the module to obtain an information carrier of a given thickness.
{circle around (4)} The information carrier is produced by a method comprising the steps of drawing off from rolls the top ends of a continuous flexible IC module, a first heat-meltable sheet and a second heat-meltable sheet which are wound on the rolls; guiding the flexible IC module and the first and second heat-meltable sheets drawn off from the respective rolls to laminating rolls to laminate individually the first and second heat-meltable sheets on the front side and the back side of the flexible IC module; guiding the laminate of the flexible IC module and the first and second heat-meltable sheets to heating-pressing rolls to compress the laminate in the thickness direction under heating, thereby to melt the first and second heat-meltable sheets; and impregnating the flexible IC module with the melt of the first and second heat-meltable sheets and roll press molding the module to obtain an information carrier of a given thickness.
{circle around (5)} The information carrier is produced by a method comprising the steps of drawing off from rolls the top ends of a continuous flexible IC module, a first heat-meltable sheet, a second heat-meltable sheet, a first cover sheet and a second cover sheet which are wound on the respective rolls; guiding the flexible IC module, the first and second heat-meltable sheets and the first and second cover sheets drawn off from the respective rolls to laminating rolls to laminate individually the first and second heat-meltable sheets on the front side and the back side of the flexible IC module and to laminate individually the first and second cover sheets on the outer surfaces of the first and second heat-meltable sheets; guiding the laminate of the flexible IC module, the first and second heat-meltable sheets and the first and second cover sheets to heating-pressing rollers to compress the laminate in the thickness direction under heating, thereby to melt the first and second heat-meltable sheets; and impregnating the flexible IC module with the melt of the first and second heat-meltable sheets and simultaneously bonding the first and second cover sheets by the melt, and roll press molding the module to obtain an information carrier of a given thickness.
The methods for the production of the information carriers mentioned in the above {circle around (2)}-{circle around (5)} have the same effects as the preceding method, and, besides, since they carry out casing of the flexible IC module by roll pressing method, the information carriers can be produced at a very high efficiency and productivity of the information carriers can be enhanced to reduce the cost.